Incontinent persons often urinate or void in a diaper or clothing rather than in a toilet causing significant discomfort and distress to the person. In addition, there is considerable expense to nursing homes for changing the diaper or clothing as well as providing these disposable supplies. The costs for such supplies and services has been estimated at 3 billion dollars per year.
Various devices have been invented to indicate when a person voids so that the person's diaper or clothing may be changed. For example, U.S. Pat. Nos. 3,460,123 of Bass, 4,271,406 of Wilson, 4,356,479 of Wilson, 4,539,559 of Kelly et al., 4,738,260 of Brown describe systems that set off an alarm after a person being monitored voids. These systems include circuits that are closed through urine. See U.S. Pat. Nos. 3,460,123 (conductor screens 30 and 32); 4,271,406 (moisture sensing electrodes 30); 4,356,479 (magnetic sensing electrodes 30); 4,539,559 (absorbent pad 2); 4,738,260 (urine sensing pad 12 and sheath 102; col. 3, lines 6-7, col. 5, lines 6-8).
U.S. Pat. No. 4,800,370 of Vetecnik describes a wetness detection system that detects dampness in a diaper or other clothing and triggers an alarm when a conductive path between conductor wires 224 is closed. The Vetecnik patent also describes an additional feature that provides a reading of the patient's temperature or "body heat." See col. 3, lines 63-65 and col. 5, lines 27-30. As shown in FIG. 3, detector/transmitter 4 is attached between the skin of a person 308 and a diaper 300 by a spring clip 204. The temperature of the skin is measured by means of a thermistor 412 (shown in FIG. 4) located inside housing 200 of detector/transmitter 4 (shown in FIG. 2). The temperature of the urine is not measured because the urine is located away from housing 200. Note that elongated conductor strip 216 (shown in FIGS. 2 and 4) travels down the diaper toward the location of the urine.
U.S. Pat. No. 4,653,491 of Okada et al. describes a system that measures the amount of wetness in a diaper by measuring capacitance. When the capacitance exceeds a limit, an alarm is set off.
A problem with the systems of each of above-cited patents is that they determine only the occurrence of urination after it has happened. The systems do not help the incontinent person to avoid the situation.
U.S. Pat. No. 4,977,906 of DiScipio describes a system including sensors 12 and 13, which are placed in an undergarment, such as a diaper. During an enuresis incidence, moisture is absorbed in the undergarment. When the undergarment is sufficiently wet, the open circuit across sensors 12 and 13 is completed resulting in an alarm being set off. The DiScipio patent states it is possible to monitor occurrences of urine discharge and determine when future occurrences are likely. The information can be used to forewarn the patient of the likelihood of a enuresis incident.
A problem with the system of the DiScipio patent is that as long as the diaper remains wet, the open circuit across sensors 12 and 13 remains completed. The system cannot recognize the situation when a person voids twice before the diaper is dry. Therefore, the predictive value of the system is limited.
There is, therefore, a need for a system that can detect urination even though the diaper of the person is wet.